The present invention relates to a method for mounting components such as electronic components, and the like on a circuit-formed substrate such as an electronic circuit board, and a component-mounting apparatus for performing this component-mounting method.
FIG. 6 shows an outline of a conventional component-mounting apparatus (1) in its entirety. In FIG. 6, the component-mounting apparatus (1) comprises, as main components: a component-feeding unit (2) composed of a cassette type component-feeding device for feeding components such as electronic components or the like; a tray-feeding unit (3) composed of a tray type component-feeding device; a mounding head (4) equipped with a plurality of nozzles for taking components out of both feeding units (2, 3) and mounting them onto a circuit-formed substrate; an XY robot (5) for carrying the mounting head (4) to a predetermined position; a component-recognition camera (6) for recording and recognizing a condition of a component held by a nozzle of the mounting head (4); a circuit-formed substrate-securing device (7) for carrying the circuit-formed substrate to the component-mounting apparatus (1) and securing the same; and a control unit (9) for controlling operations of the component-mounting apparatus in its entirety.
With reference to FIG. 6, a cassette type component-feeding device (8) having a reel, onto which a lot of components are tape-like wound up, is set on the component-feeding unit (2). A tray pallet type component-feeding device (10), on which a lot of components are arrayed, is set on the tray-feeding unit (3). The mounting head (4) is equipped with nozzle heads (11) each having a nozzle (12) for sucking and removing a component (13) from the component-feeding unit (2) or the tray-feeding unit (3). An angle of each nozzle (12) can be corrected by rotating the nozzle on an axis Z by use of a rotation-controlling mechanism (0 rotation). The X-Y robot (5) carries the mounting head (4) on a plane in X- and Y-directions. The circuit-formed substrate-securing device (7) carries and secures the circuit-formed substrate (14) such as an electronic circuit substrate or the like. The mounting head (4) is equipped with a substrate-recognition camera (15) for recording and recognizing a condition of the circuit-formed substrate when secured.
The component-mounting apparatus (1) thus constructed is operated as follows. The mounting head (4) moves just above a component (13) fed by the component-feeding unit (2) or the tray-feeding unit (3), and causes each of the nozzles (12) to lower such that one of the nozzles contacts and sucks the component (13) and removes it from the component-feeding unit (2) or the tray-feeding unit (3), utilizing a negative pressure. Next, the mounting head (4), sucking and holding the component (13) with the one of the nozzles (12), is carried by the X-Y robot (5) to a position facing to the component-recognition camera (6). The component-recognition camera (6) records and recognizes the component (13) sucked and held by nozzle (12) of the mounting head (4) while the mounting head (4) is passing through a position facing the component-recognition camera (6) at a predetermined speed. An inclination of the component (13) and a dislocation of a position thereof are measured based on a result of the above recognition.
The circuit-formed substrate (14) is carried by the circuit-formed substrate-securing device (7) and then regulated and secured at a predetermined position. When the mounting head (4) is moved to a position facing the circuit-formed substrate (14), the substrate-recognition camera (15) provided on the mounting head (4) records and recognizes the circuit-formed substrate (14). An inclination or dislocation of the circuit-formed substrate (14) is measured based on a result of this recognition. The control unit (9) sends, to each of the nozzle heads (11) mounted on the mounting head (4), a correction amount of the position and inclination of the component (13) based on the position, inclination and dislocation of the circuit-formed substrate (14). The nozzle head (11) of the one nozzle corrects a position and inclination of the component (13) according to this instruction, and then mounts the component (13) at a predetermined position on the circuit-formed substrate (14).
FIG. 7A is a view through the substrate-recognition camera (15) provided on the mounting head (4), showing a condition of the circuit-formed substrate (14) when regulated and secured. In this regard, one sheet of circuit-formed substrate (14) may compose a single electronic circuit substrate. However, in association with recent electronic devices with small sizes and light weight, downsizing of electronic circuit substrates is demanded, and thus, in many cases, a single circuit-formed substrate (14) is sectioned to provide a plurality of electronic circuit substrates as shown in FIG. 7A. In the example shown in FIG. 7A, the circuit-formed substrate (14) is sectioned for nine individual substrates (16a) to (16i) which are arrayed in three rows and three columns. It may be sectioned for more individual substrates, for example, several tens of substrates. In the present specification, one entire sheet with an original size is referred to as the circuit-formed substrate (14), and any of specified and individual substrates (16a) to (16i) is denoted by using an individual reference number or notation. Further, when not a specified individual substrate but a plurality of individual substrates provided from one circuit-formed substrate are generally referred to, such individual substrates are called individual substrates (16).
As shown in FIG. 7A, generally, a pair of reference marks (21) are provided at and around corners on a diagonal line of the circuit-formed substrate (14). The substrate-recognition camera (15) recognizes both reference marks (21) of the circuit-formed substrate (14) while being regulated and secured by the circuit-formed substrate-securing device (7), and an inclination of the circuit-formed substrate (14) and dislocation of a position thereof are measured based on a result of this recognition. The inclination of the circuit-formed substrate (14) and the dislocation of the position thereof are included in correction amounts for the inclination of the component (13) and the dislocation of the position thereof when the component (13) is mounted.
On the other hand, generally, a pair of individual substrate marks (22) are provided at and around corners of a diagonal line of each of the individual substrates (16). The component (13) itself becomes smaller in association with downsizing of electronic devices as mentioned above, and thus, a component-mounting density becomes higher. Therefore, it is required to accurately mount components at predetermined positions without any interference from other components which have already been mounted. The individual substrate marks (22) are used to perform accurate positioning of components on each individual substrate (16).
In addition to the individual substrate marks (22), a position for indicating a bad mark (23) is provided on the individual substrate (16). If some factors for failure, such as incorrect mounting or non-mounting, occur on a specified individual substrate (16) during any step of a process of mounting components onto the circuit-formed substrate (14), a bad mark (23) is indicated on a relevant individual substrate (16). Generally, an operator or an automatic machine provides a bad mark (23) by coloring it using black ink or the like when finding a failure in the course of an intermediate inspection step or the like. This bad mark (23) is recognized by the substrate-recognition camera (15) based on an occupation ratio of brightness (white and black are grasped based on their proportion by a binary value level). An individual substrate (16) attached with the bad mark (23) does not undergo a later component-mounting process so as to save useless consumption of components and loss of tact time.
Arrows of a broken line shown in FIG. 7A indicate a passage along which the substrate-recognition camera (15) recognizes bad marks (23). This recognition passage starts from a recognition of bad mark (23) on individual substrate (16a), followed by bad marks (23) on other individual substrates (16b, 16c) in the same row, further followed by bad mark (23) on individual substrate (16d) in a next row, and the recognition is performed in the same manner up to final individual substrate (16i). In the example shown in FIG. 7A, bad marks (23) are put on the individual substrates (16a, 16c, 16e, 16h, 16i), respectively. FIG. 7B shows a passage of recognizing the individual substrate marks (22) after recognition of the bad marks (23). Also, in this recognition passage, as indicated by arrows of broken lines, first, a pair of individual substrate marks (22) of the individual substrate (16a) are recognized, followed by individual substrate marks (22) of the individual substrates (16b) to (16i) in order.
FIG. 8 shows a flowchart of a recognition operation performed by the substrate-recognition camera (15). In FIG. 8, the substrate-recognition camera (15) is moved to a position facing the circuit-formed substrate (14) in accordance with movement of the mounting head (4), and the substrate-recognition camera (15) first recognizes the reference marks (21) at two positions of the circuit-formed substrate (14) at Step 51. During an actual recognition operation, the substrate-recognition camera (15) first takes up an image of reference mark (21) at a first point into CCD. This image is inputted to the control unit (9) and stored therein. Next, the camera (15) recognizes an image of reference mark (21) at a second point and takes it into CCD and inputs this image to the control unit (9) and stores it therein. An inclination of the circuit-formed substrate (14) and a dislocation of a position thereof are measured based on a result of recognition of both reference marks (21) at the two points. Next, at Step 52, the camera (15) sequentially recognizes the bad marks (23) on the individual substrates (16) provided by sectioning the circuit-formed substrate (14) (nine total points in the example shown in FIGS. 7A and 7B). As mentioned above, data of the individual substrates (16) on which the bad marks (23) have been recognized are inputted to the control unit (9) so as not to undergo a later component-mounting step.
Next, at Step 53, the substrate-recognition camera (15) sequentially recognizes paired individual substrate marks (22) on overall individual substrates (16) provided by sectioning the circuit-formed substrate (14) (eighteen points in total in the example shown in FIGS. 7A and 7B). Results of this recognition of the individual substrate marks (22) are inputted to the control unit (9) so as to be reflected on correction amounts for an inclination and a position of a component to be mounted during a later component-mounting step. After that, the component-mounting operation is performed at Step 54, and the components (13) sucked by each of the nozzles is mounted on a predetermined position of each of the individual substrates (16).
However, the conventional component-mounting method as mentioned above has problems as follows. That is, during the operation of recognizing the individual substrates (16), first, recognition of the bad marks (23) is performed (Step 52 of the flowchart shown in FIG. 8), followed by recognition of the individual substrate marks (22) (Step 53 of the same flowchart), and therefore, many recognition operations as a whole are required, and much time is required for performance of these many recognition operations, which may adversely influence a case of a circuit-formed substrate (14) which is sectioned into several tens of individual substrates. For example, in case of a circuit-formed substrate (14) sectioned into seventy-seven individual substrates, as many as two hundred thirty one recognition operations in total are required for a single circuit-formed substrate (14).
Next, the inclination of the circuit-formed substrate (14) and dislocation of the position thereof are recognized based on results of recognition of a pair of reference marks (21) on the circuit-formed substrate (14), and results of this recognition are used in calculation of correction amounts for inclination of component (13) and a position thereof. However, a recognition error may occur in the course of the operation of recognizing the individual substrate marks (22) on each of the individual substrates (16), depending on a degree of inclination of the circuit-formed substrate (14), and thus, in some cases, a result of recognition of the reference marks (21) of the circuit-formed substrate is not effectively utilized. FIG. 9 shows one of such situations, in which, as indicated by an arrow of broken line (25), a pair of reference marks (21) of the circuit-formed substrate (14) is first recognized by the substrate-recognition camera (15), and the inclination of the circuit-formed substrate (14) and dislocation of the position thereof are measured based on results of this recognition. These results are used for calculation of correction amounts for the inclination of a component (13) to be mounted and dislocation of the position thereof.
In review of each of the individual substrates (16), for example, recognition of the individual substrate marks (22) of the individual substrates (16a, 16b) has no failure because the individual substrate marks (22) of the individual substrates (16a, 16b) are included in visual field (31) of the substrate-recognition camera (15). In contrast, for example, in case of individual substrate (16c), a component of individual substrate mark (22) indicated by a circle is excluded from the visual field (31) of the camera (15) indicated by a square, which results in a recognition error. Such recognition errors similarly occur in case of the individual substrates (16f, 16g, 16h, 16i). If such a recognition error occurs, the following process may be optionally determined. However, correction amounts for the inclination and position of a component (13) cannot be determined if such a recognition error is left unresolved. Therefore, the individual substrates (16) having such recognition errors have conventionally been judged as defectives. The individual substrates (16) judged as defectives are not subjected to a following component-mounting step. In other words, the individual substrates (16) which may be originally non-defectives are judged as defectives and are scrapped, depending on inclination of the circuit-formed substrate (14).
To solve the problem induced by the above recognition error, it is proposed to widen the visual field of the substrate-recognition camera (15). However, this solution has a problem in that, generally, resolution of the camera degrades if the visual field of the camera is widened, which leads to a further problem in that tact time becomes longer because recognition of an individual substrate requires a longer time. In addition, there is a danger of degrading accuracy of recognition determined by an occupation rate of brightness mentioned above, because, by widening the visual field of the camera (15), other factors may be included in the visual field of the camera (15) and because such factors may be recognized by mistake. At present, on the contrary, there is a tendency of narrowing the visual field of a recognition camera to improve resolution of the camera and to thereby reduce recognition time, so as to improve production efficiency. However, narrowing the visual field means more frequent occurrence of the foregoing recognition errors, which leads to a decrease in a yield of non-defectives.
Objects of the present invention are, therefore, to provide a component-mounting apparatus which is free from the above problems during recognition operations of the circuit formed substrate (14) of the conventional apparatus, and which can perform efficient recognition operations to increase a yield of non-defectives and to thereby improve productivity, and to provide a component-mounting method.